1. Field of the Invention
The present invention relates to a projection type display device that displays an image on the basis of projection of a light modulated by a light valve.
2. Related Background Art
Projection type display devices of various structures have hitherto been proposed which display an image on the basis of projection of a light modulated by a light valve such as a liquid crystal panel.
One of such projection type display devices rotatively drives a color wheel to spectrally separate a white light and utilizes the separated light to achieve color display. FIG. 3 is a schematic view showing an example of a structure of a conventional projection type display device. In this figure, reference numerals 1, 1a and 1b denote a projection lamp, a lamp bulb, and an ellipsoidal reflector, respectively. Reference numerals 2, 3, 3a and 3b denote a color wheel, a rod integrator lens, an entrance end face, and an exit end face, respectively. Reference numerals 4, 5, 10, 11 and 12 denote a relay lens, a field lens, a light valve, a projection lens, and a housing, respectively. Reference characters m, M and A1 denote an axis of rotation, a motor, and an optical axis, respectively. Reference characters L11, L12 and D3 denote an exiting light, an exiting light and a projection type display device, respectively.
The projection type display device D3 comprises the projection lamp 1 that emits a white light. The projection type display device D3 has the following components sequentially arranged on its light emission side:
the color wheel 2 that sequentially separates the white light into respective colors on the basis of rotative driving effected by the motor M;
the rod integrator lens (hereinafter referred to as xe2x80x9crod lensxe2x80x9d) 3 used to optimally irradiate a display area of the light valve 10 with the light;
the relay lens 4;
the field lens 5;
the light valve 10 that modulates the irradiation light; and
the projection lens 11 that enlarges and projects the light modulated by the light valve 10, on a screen (not shown).
FIG. 4 is a sectional view showing the structure of the projection lamp 1 in detail. As shown in this figure, the projection lamp 1 is composed of the lamp bulb 1a and the ellipsoidal reflector 1b placed behind the lamp bulb 1a. The ellipsoidal reflector 1b has a reflecting surface shaped like an ellipsoidal surface (see reference character R1) that is rotationally symmetric with respect to the optical axis A1. The ellipsoidal reflector 1b has two focuses (hereinafter referred to as xe2x80x9cfirst focus F1xe2x80x9d and xe2x80x9csecond focus F2xe2x80x9d). The lamp bulb 1a (to be exact, its portion that emits light) is placed at the first focus F1.
Further, as shown in FIG. 5, the color wheel 2 is divided into a plurality of color filter sections 2R, 2G and 2B (for example, three color filter sections for red, blue, and green or four color filter sections for red, blue, green, and transparency). The color wheel 2 is rotatively driven by the motor M to sequentially separate the white light spectrally.
Furthermore, the rod lens 3 is an optical element shaped like a square pole and is formed of transparent glass or a resin material. The side surfaces (i.e., surfaces other than the entrance end face 3a and exit end face 3b) of the rod lens are each a total reflection surface. Further, reference numeral 12 denotes the housing.
When the projection lamp 1 is energized, the emitted light L11 is condensed by the ellipsoidal reflector 1b and then spectrally separated by the color wheel 2. The region of the light L11 that has got out of the projection lamp 1 is represented by a triangle including two sides shown by dotted lines in FIG. 4. That is, the region is a triangle region including two dotted lines that cross at the second focus F2 of the four dotted lines shown in FIG. 4. Subsequently, the light enters the rod lens 3 through the entrance end face 3a and is then totally reflected by the side surface of the rod lens 3 (or exits through the exit end face 3b without being totally reflected) to form a uniform light. The exiting light L12 passes through the relay lens 4 and the field lens 5 to produce a flux of parallel light, which then passes through the light valve 10 to be thereby converted into an optical image, which then passes through the projection lens 11 to be finally projected on the screen (not shown).
FIG. 6 shows a projection type display device D4 of another configuration. As shown by reference numeral 6 in FIG. 6, a total reflection mirror is placed above the projection lamp 1. This device is adapted to reflect a light from the projection lamp 1, from a direction along an optical axis A1 to a direction along an optical axis A2.
However, with the projection type display device D4 of the structure shown in FIG. 6, the color wheel 2 or the motor M may interfere with the ellipsoidal reflector 1b or may block the light L11 irradiated to the ellipsoidal reflector 1b by the lamp bulb 1a. This is because, as shown in the figure, the color wheel 2 is partly located in the triangular region of the light L11 getting out of the projection lamp 1.
To obviate this problem, a projection type display device D5 of another configuration has been proposed. This is shown in FIG. 7. As shown in the figure, when the color wheel 2 and the motor M are placed above the optical axis A2, a sufficient space must be provided above the optical axis A2, which poses another problem that the size of the device will increase.
It is, therefore, an object of the present invention to provide a projection type display device that is free from the above problems.
The present invention has been accomplished in view of the above circumstances and provides a projection type display device comprising a light source for emitting a white light, a reflecting means for reflecting the emitted light, a color wheel comprising a plurality of color filter sections of different colors for sequentially separating the light from the light source into different colors on the basis of rotative driving, and a light valve for modulating the separated light, the light from the light source being separated by the color wheel, modulated by the light valve and then projected, wherein the color wheel is disposed in an area interposed between a light entering (or incident on) the reflecting means and a light exiting the reflecting means such that the light from the light source passes through the color wheel in such a converged shape as to pass through only a single color filter section.